In a color filter used for a liquid crystal display device, a light-shielding film called a black matrix is arranged for the purposes of shielding light between colored pixels, increasing contrast and the like. Further, in a solid-state image pick-up element, a black matrix is also arranged for the purposes of preventing noise and increasing image quality and the like. The black matrix is manufactured by forming a pattern using photolithographic methods or the like by using a polymerizable composition containing a dispersion composition, in which a light-shielding black colorant is dispersed, a polymerizable compound, a polymerization initiator, and other components.
As a composition for forming a black matrix for a liquid crystal display device or for a solid-state image pick-up element, a photosensitive resin composition containing a black colorant such as carbon black or titanium black is known.
As a black matrix for a liquid crystal display device, a black matrix is required that has high light-shielding property in order to increase contrast and improve visibility. On the other hand, as a black matrix for a solid-state image pick-up element, it is also necessary that the black matrix have light-shielding property in the infrared region in addition to the light-shielding property in the visible region.
Conventionally, in light-shielding black matrices, carbon black has generally been used. However, when an increase in the light-shielding property of a black matrix is attempted using carbon black, it is necessary to increase the amount of or use a large amount of carbon black in the black matrices. Accordingly, a dispersion composition or polymerizable composition having a high concentration of carbon black serving as a light-shielding material is required for forming a light-shielding pattern. However, when the content of carbon black is increased in order to achieve a high light-shielding effect, problems arise whereby carbon black particles are insufficiently dispersed in the dispersion, and pattern formability is impaired.
Further, it is required that there is minimal residue of the composition in an unexposed region after development, and that a coated film when the composition is coated on a substrate is even, and further, that a favorable shape is formed; specifically, it is desirable that no difference in the thickness of the light-shielding film (i.e., no step) is generated between the peripheral region thereof and the central region thereof.
In a black matrix for a liquid crystal display device, the light-shielding effect is mainly required in the visible region, whereas in a black matrix for a solid-state image pick-up element, a light-shielding effect in the infrared region is required in addition to a light-shielding effect in the visible region.
Further, a black matrix for a liquid crystal display device is required to be micronized, whereas a black matrix for a solid-state image pick-up element (in particular, a black matrix for shielding the surface at the opposite side of a support from a light receiving element-forming surface (hereinafter, also referred to as the “back surface”)) is required to be configured to uniformly shield a wider area than that of a black matrix for a liquid crystal display device.
When a light-shielding film having a large area is formed as a light-shielding film for a solid-state image pick-up element using a conventional photosensitive resin composition, the thickness at the peripheral region of the light-shielding film is thinner than the thickness at the central region of the light-shielding film; that is, a step is formed, which leads, in some cases, to lower light-shielding performance at the peripheral region of the light-shielding film.
Further, there has been a problem whereby when the content of the black colorant is increased in order to obtain high light-shielding property, residue tends to be generated at the peripheral region of the light-shielding film, which leads to lower sensitivity. Furthermore, there has been a problem whereby when the amount of a polymerization initiator is increased in order to increase sensitivity, the stability over time deteriorates.
In recent years, compact and thin image pick-up units are mounted on the mobile terminals of electronic devices such as mobile phones or PDAs (personal digital assistants).
Such image pick-up units are generally equipped with a solid-state image pick-up element such as a CCD (charge coupled device) image sensor, a CMOS (complementary metal oxide semiconductor) image sensor, or the like, and a lens for forming object images on the solid-state image pick-up element.
Miniaturization and thinning of the image pick-up units are demanded in conjunction with the miniaturization and thinning of mobile terminals. Further, in order to reduce the cost of the mobile terminals, an increase in the efficiency of the production process is desired. As a method of manufacturing a large number of such miniaturized lenses, a method of manufacturing a lens module is known in which a wafer level lens having a configuration obtained by forming plural lenses on a substrate is manufactured, and the substrate is cut so that the plural lenses are separated into the respective lenses.
Further, a method of manufacturing an image pick-up unit is known where a substrate having plural lenses formed thereon is integrally combined with a sensor substrate having plural solid-state image pick-up elements thereon, and the substrate and the sensor substrate are cut so as to include a lens and a solid-state image pick-up element as a set.
Hitherto, as a wafer level lens, a multilayered wafer level lens formed by superimposing substrates having plural lenses thereon has been disclosed (for example, refer to Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-539276). The wafer level lens is formed from a substrate and a lens made of transparent materials that are light transmissive, and light can transmit through any region of the wafer level lens; therefore, there is a possibility that in a case in which the wafer lens is diced and the diced lens is mounted to an image pick-up element to form an image pick-up unit, optical performance defects such as ghosting or flaring easily occur at the time of image pick-up when light transmission or light reflection occurs in regions other than the lens surface of the lens. From the viewpoint of preventing such defects regions other than the lens of a wafer level lens, for example, are subjected to processing such as formation of a light-shielding member.
Further, a method, in which a molding material is supplied onto a substrate to form a lens by using a mold on the substrate, has been disclosed (for example, refer to International Publication No. WO 2007/107025).
In order to meet these quality requirements for a black matrix with high light-shielding property as described above, the usefulness of titanium black having high light-shielding property is recognized, and various methods for improving the dispersibility of titanium black have been proposed (for example, see Japanese Patent Application Laid-Open (JP-A) Nos. 10-246955, 9-54431, 10-46042, 2007-115921, 10-114836, 2002-275343 and 2005-266189).